Philippa Kaur

BALTIMORE — When the James Webb Space Telescope was first dreamed up, exoplanets hadn’t even been discovered yet. Now the observatory is showing astronomers what it can learn about planets orbiting other stars — including the small ones.

Since its launch in December 2021, JWST had already “sniffed” the atmospheres of Jupiter-sized planets orbiting searingly close to their stars (SN: 8/26/22). Those intense worlds are interesting, but not the places where astronomers hope to look for signs of life. The telescope is now getting glimpses of atmospheres on known exoplanets of the more terrestrial persuasion, astronomers reported December 13 and 14 at the First Science Results from JWST conference.

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And JWST is starting to find new rocky worlds too.

These early peeks at far-off worlds don’t yet reveal a lot about these remote locales. But researchers are buoyed by what JWST’s sharp vision in infrared wavelengths could eventually unearth about the smaller planets beyond our solar system.

“The main message is, we’re in business,” said University of Montreal astronomer Björn Benneke. “We don’t even have all the observations yet, but they are already quite exciting.”

One of the smaller planets that JWST looked at is GJ 1214b, which has frustrated astronomers since its discovery in 2009 (SN: 12/16/09). The planet is a sub-Neptune, meaning its size is somewhere between that of a rocky world like Earth and a gaseous one like Neptune.

“What the heck are sub-Neptunes?” asked astronomer Eliza Kempton of the University of Maryland in College Park. They could be balls of rock with thick hydrogen and helium atmospheres, or maybe water worlds (SN: 2/22/12). “What we’d like to do with atmospheric characterization is measure their atmospheres and see which is which,” Kempton said.

Previously, astronomers tried to observe the makeup of GJ 1214b’s atmosphere by watching how starlight filtered through it. But the atmosphere is thick and hazy, blocking astronomers’ ability to detect individual molecules in it.

Instead of watching the planet pass in front of its star, Kempton and colleagues used JWST to look for the glow of the planet right before it disappeared behind the star. And it worked: After 38 hours of observing, the researchers detected the planet’s infrared glow, Kempton said in a December 13 presentation.

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There’s more work to do, but the initial data suggest the planet has a lot of chemical components, possibly including water and methane. It’s also enriched in elements heavier than hydrogen and helium.

As for knowing what kind of world GJ 1214b is, “I’d say we’re not quite there yet,” Kempton said. It could be a watery planet, she said, or a gassy planet that has lost a fair amount of its lighter elements.

The telescope also had its first look at the tantalizing TRAPPIST-1 system, Benneke said in a different December 13 presentation (SN: 12/13/17). Discovered in 2017, the system contains seven Earth-sized worlds that are probably rocky. Three of those planets might have the right temperatures for liquid water to exist on their surface, making them particularly interesting targets for JWST and other telescopes to look for signs of life.

But TRAPPIST-1 is a small, red star called an M dwarf, a type of star that is notorious for violent flares and strong radiation. For years, astronomers have debated whether planets around these stars would be hospitable to life, or if the stars would strip their planets’ atmospheres away (SN: 6/14/17).

“If the TRAPPIST planets don’t have atmospheres, then we need to move on” from M dwarfs in the search for extraterrestrial life, says astronomer Mercedes Lόpez-Morales of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., who was not involved in the new JWST observations.

JWST’s first look at one of those potentially habitable worlds, TRAPPIST-1g, did not reveal any clear signs of an atmosphere. But the telescope looked at the planet for only about five hours. With more observations, an atmosphere should be detectable if it’s there, Benneke said.

JWST is getting into the planet-hunting game too, said astronomer Kevin Stevenson on December 14. The telescope double-checked a potentially interesting observation from another telescope and confirmed that it had seen a rocky, Earth-sized world around a nearby M dwarf. This proves that JWST has the precision to find such worlds.

“It is an exciting result, perhaps the first discovery of an exoplanet by JWST,” said Stevenson, of the Space Telescope Science Institute in Baltimore. The planet orbits its dim star every two days, so it’s probably around 225° Celsius on the surface — likely too hot to be habitable, he says. “It’s more like an exo-Venus than an exo-Earth.”

While it’s still early days, the researchers emphasized, the forecast for planet hunting using JWST is good.

The results are paving the way for future observatories too, said astrophysicist John Mather of NASA’s Goddard Space Flight Center in Greenbelt, Md. Astronomers’ wish list for future missions includes a telescope that can dig even further into the details of potentially habitable worlds.

“If it’s not impossible,” Mather said, “let’s do it.” More

The first planet ever spotted by the Kepler space telescope is falling into its star.

Kepler launched in 2009 on a mission to find exoplanets by watching them cross in front of their stars. The first potential planet the telescope spotted was initially dismissed as a false alarm, but in 2019 astronomer Ashley Chontos and colleagues proved it was real (SN: 3/5/19). The planet was officially named Kepler 1658b.

Now, Chontos and others have determined Kepler 1658b’s fate. “It is tragically spiraling into its host star,” says Chontos, now at Princeton University. The planet has roughly 2.5 million years left before it faces a fiery death. “It will ultimately end up being engulfed. Death by star.”

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The roughly Jupiter-sized planet is searingly hot, orbiting its star once every three days. In follow-up observations from 2019 to 2022, the planet kept transiting the star earlier than expected.

Combined data from Kepler and other telescopes show that the planet is inching closer to the star, Chontos and colleagues report December 19 in the Astrophysical Journal Letters.

“You can see the interval between the transits is shrinking, really slowly but really consistently, at a rate of 131 milliseconds per year,” says astrophysicist Shreyas Vissapragada of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

That doesn’t sound like much. But if this trend continues, the planet has only 2 million or 3 million years left to live. “For something that’s been around for 2 to 3 billion years, that’s pretty short,” Vissapragada says. If the planet’s lifetime was a more human 100 years, it would have a little more than a month left.

Studying Kepler 1658b as it dies will help explain the life cycles of similar planets. “Learning something about the actual physics of how orbits shrink over time, we can get a better handle on the fates of all of these planets,” Vissapragada says. More

BALTIMORE — The James Webb Space Telescope is living up to its promise as a wayback machine. The spectacularly sensitive observatory is finding and confirming galaxies more distant, and therefore existing earlier in the universe’s history, than any seen before.

The telescope, also known as JWST, has confirmed extreme distances to four galaxies, one of which sets a record for cosmic remoteness by shining about 13.475 billion years ago, astronomers reported December 12 at the First Science Results from JWST conference. Dozens of other galaxies may have been spotted as they were just 550 million years or less after the Big Bang, meaning the light from those galaxies traveled at least 13.1 billion years before reaching the telescope.

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Taken together, the new observations suggest galaxies formed earlier and faster than previously thought. “We’re entering a new era,” says astronomer Swara Ravindranath of the Space Telescope Science Institute in Baltimore.

That new era is thanks in part to JWST’s ability to see very faint infrared light (SN: 10/6/21). For the most distant objects, like the first stars and galaxies, their visible light is stretched by the relentless expansion of the universe into longer infrared wavelengths that are invisible to human eyes and some previous space telescopes. But now, measurements that were recently impossible are suddenly easy with JWST, researchers say.

“JWST is the most powerful infrared telescope that has ever been built,” astrophysicist Jane Rigby said at the conference. Rigby, of NASA’s Goddard Space Flight Center in Greenbelt, Md., is the JWST operations project scientist. “Almost across the board, the science performance is better than expected.”

Even in the very first image, released in July, astronomers spotted galaxies whose light originated 13 billion years ago or more (SN: 7/11/22). But those distances were estimates. To measure the distances precisely, astronomers need spectra, measurements of how much light the galaxies emit across many wavelengths. Those measurements are slower and more difficult to make than pictures.

“Thanks to this glorious telescope, we’re now getting spectra … for hundreds of galaxies at once,” said astronomer Emma Curtis-Lake of the University of Hertfordshire in England.

Among those are four of the earliest galaxies ever seen, some of which existed less than 400 million years after the Big Bang, Curtis-Lake and colleagues reported at the meeting and in a paper submitted December 8 to arXiv.org. The team spotted these record holders in a patch of sky that the Hubble Space Telescope once scoured for ultra-remote galaxies (SN: 1/3/10).

The previous distance record holder existed between 13.3 billion and 13.4 billion years ago, or about 400 million years after the Big Bang (SN: 1/28/20). JWST confirmed the distance to that galaxy and came back with three more whose light comes from as early as 325 million years after the Big Bang.

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The galaxies are also surprisingly pristine, chemically speaking, lacking in elements heavier than hydrogen and helium.

“We don’t see that in the present-day universe,” says Ravindranath, who was not involved in the new discovery. It could mean that not many of the galaxies’ stars have died in supernova explosions that spread heavy elements around the universe, which suggests the galaxies’ original stars were not extremely massive.

In another part of the sky, JWST has spotted 26 galaxies that may have existed about 550 million years or earlier after the Big Bang, astronomer Steven Finkelstein and colleagues reported at the meeting and in a paper submitted November 10 to arXiv.org.

“On an emotional, visceral level, looking at these images is amazing,” said Finkelstein, of the University of Texas at Austin.

The first of these to be discovered, dubbed Maisie’s Galaxy after Finkelstein’s daughter, appears to be just 380 million years after the Big Bang, the researchers reported December 1 in the Astrophysical Journal Letters. The most distant galaxy in the team’s survey might lie as much as 130 million years earlier than Maisie. Those galaxies’ distances still need to be confirmed with spectra, but the team expect to get those data in the next few weeks.

This fuzzy red dot in the inset box at right is Maisie’s Galaxy as seen with JWST. If new measurements of the wavelengths of light it is emitting confirm its distance, astronomers may be seeing this galaxy as it was less than 400 million years after the Big Bang.NASA, STScI, CEERS, TACC, S. Finkelstein, M. Bagley, Z. Levay

And distant galaxies that lie behind a massive galaxy cluster called Abell 2744 are also more numerous and distant than expected, astrophysicist Guido Roberts-Borsani of UCLA said at the meeting.

Before JWST observed the cluster, astronomers predicted it should find effectively zero galaxies from 13.2 billion years ago. “But we found two,” said Roberts-Borsani, who reported the results at the meeting. “So something’s a little bit weird.” It could mean that galaxies form earlier and faster than thought, he said, although it could also mean that JWST was just looking at a particularly galaxy-rich patch of the sky.

All these new galaxies are exciting because they could be responsible for making the universe transparent to visible light, a process astronomers call reionization (SN: 12/2/22). Before the first stars ignited, the universe was filled with a hot dense soup of particles. The first stars and galaxies bathed the universe in ultraviolet light, splitting electrons off hydrogen atoms and allowing light to zip through until it reached JWST.

The new data, Roberts-Borsani said, “give us constraints on when this process started, ended, and which galaxies were the culprits for this process.” More